Electrical assembly

Abstract

An electrical assembly comprises a device. The device includes an inductive coil and an armature. The armature is arranged to be moveable between first and second positions when the inductive coil is energized. The electrical assembly further includes a detection unit which is configured to detect an inductance of the inductive coil or a characteristic that corresponds to the inductance of the inductive coil. The detection unit is further configured to determine the position of the armature based on the detected inductance or the detected characteristic.

What we claim is: 
     
       1. An electrical switching assembly comprising:
 a switching device including an inductive coil, an armature, and a movable contact, the armature arranged to be moveable between first and second positions when the inductive coil is energized, and the armature being configured to permit movement of the moveable contact, the inductive coil forming part of an input circuit, and the armature, and the moveable contact forming part of an output circuit operating at higher current than the input circuit; 
 a detection unit configured to detect an inductance of the inductive coil or a characteristic that corresponds to the inductance of the inductive coil, the detection unit further configured to determine a position of the armature based on the detected inductance or the detected characteristic, wherein the detection unit is configured to compare the detected inductance or detected characteristic with a single reference inductance threshold or reference characteristic threshold to determine the position of the armature; and 
 a calibration unit configured to carry out a calibration of the switching device so as to determine the single reference inductance or reference characteristic threshold, wherein the single reference inductance or reference characteristic threshold is indicative of the armature being half-way between the first and second positions. 
 
     
     
       2. The electrical switching assembly according to  claim 1 , further including a control unit configured to selectively control a voltage across the inductive coil so as to apply a voltage step to the inductive coil, wherein the detection unit is configured to detect the inductance of the inductive coil or the characteristic that corresponds to the inductance of the inductive coil in response to the voltage step applied to the inductive coil by the control unit. 
     
     
       3. The electrical switching assembly according to  claim 2 , wherein, when the detection unit is configured to detect the characteristic that corresponds to the inductance of the inductive coil, the detection unit is configured to monitor a rate of change of current of the inductive coil when the voltage step is applied to the inductive coil. 
     
     
       4. The electrical switching assembly according to  claim 2 , wherein the control unit is configured to control the magnitude of the voltage step applied to the inductive coil so that the voltage across the inductive coil is controlled at a first value that maintains the position of the armature. 
     
     
       5. The electrical switching assembly according to  claim 4 , wherein the magnitude of the voltage step applied to the inductive coil is controlled so that the voltage across the inductive coil is controlled at a second value lower than the voltage required to move the armature between the first and second positions. 
     
     
       6. The electrical switching assembly according to  claim 4 , wherein the magnitude of the voltage step applied to the inductive coil is controlled so that the voltage across the inductive coil is controlled at a third value equal to or higher than the voltage required to move the armature between the first and second positions and wherein the control unit is configured to control the voltage across the inductive coil so as to apply the voltage step to the inductive coil for an amount of time less than the time required to move the armature between the first and second positions at the third value. 
     
     
       7. The electrical switching assembly according to  claim 1 , wherein the calibration unit is configured to determine a first reference inductance or reference characteristic threshold indicative of the armature being in the first position, and/or a second reference inductance or reference characteristic threshold indicative of the armature being in the second position. 
     
     
       8. The electrical switching assembly according to  claim 7 , wherein, when the calibration unit is configured to determine the first and second reference inductance or reference characteristic thresholds, the calibration unit is configured to determine a third reference inductance or reference characteristic threshold that is a value between the first and second reference inductance or reference characteristic thresholds, preferably wherein the third reference inductance or reference characteristic threshold is an average of the first and second reference inductance or reference characteristic thresholds. 
     
     
       9. The electrical switching assembly according to  claim 1 , wherein the single reference inductance or reference characteristic threshold is predetermined, and is stored and/or hardcoded into the switching device. 
     
     
       10. The electrical switching assembly according to  claim 1 , wherein the device is a latching relay, the latching relay being configured to selectively hold the position of the armature when the inductive coil is de-energized. 
     
     
       11. The electrical switching assembly according to  claim 1 , wherein the switching device is a non-latching relay. 
     
     
       12. A method of determining a position of an armature of a switching device, the switching device further including an inductive coil, an armature, and a moveable contact, the armature being arranged to be moveable between a first position and a second position when the inductive coil is energized, the armature being configured to permit movement of the moveable contact, the inductive coil forming part of an input circuit, and the armature, and the moveable contact forming part of an output circuit operating at higher current than the input circuit, the method comprising:
 i) detecting an inductance of the inductive coil or a characteristic that corresponds to the inductance of the inductive coil; 
 ii) carrying out a calibration of the switching device so as to determine a single reference inductance or reference characteristic threshold, wherein the single reference inductance or reference characteristic threshold is indicative of the armature being half-way between the first and second positions; and 
 iii) determining the position of the armature based on the detected inductance or the detected characteristic by comparing the detected inductance or detected characteristic with a respective single reference inductance threshold or reference characteristic threshold to determine the position of the armature.